20 October 2018, Volume 42 Issue 10

    

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  Research Progress on Low Temperature Surface Carburization Technique of Austenite Stainless Steel

  JIANG Yong, LI Yang, CHEN Yefeng, GONG Jianming

  Materials For Mechanical Engineering. 2018, 42(10): 1-7. https://doi.org/10.11973/jxgccl201810001

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  Low temperature surface carburization of austenite stainless steel is reviewed in terms of the classification and development of low temperature surface carburization technique, and the effects of low temperature surface carburization treatment on the surface microstructure, the mechanical properties, wear resistance, corrosion resistance and hydrogen embrittlement resistance of the stainless steel. The problems and the research direction in future of the low temperature surface carburization technique of austenite stainless steel are also discussed.
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  Effect of SiO₂ with Different Specific Surface Areas on Rheological Properties and Sedimentation Stability of Magnetorheological Fluid

  GUO Qiuyue, WANG Jiong, OUYANG Qing

  Materials For Mechanical Engineering. 2018, 42(10): 8-12. https://doi.org/10.11973/jxgccl201810002

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  Magnetorheological fluids were prepared by using carbonyl iron as magnetic particles and SiO₂ nanoparticles with different specific surface areas (150, 200, 380 m²·g^-1) as thixotropic agent. The effects of SiO₂ with different specific suface areas on the rheological properties and sedimentation stability of magnetorheological fluids were studied. The results show that the larger the specific surface area of SiO₂, the greater the saturation magnetization and the relative permeability of the magnetorheological fluid. With the increase of the specific surface area of SiO₂, the off-state viscosity of the magnetorheological fluid increased rapidly and then decreased slightly, and the the shear stress, yield stress and sedimentation stability increased. When the specific surface area of the SiO₂ was 380 m²·g^-1, the magnetorheological fluid showed an excellent controllability.
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  Microstructure and Properties of SiC Ceramic Joint Actively Brazed with SiC_p Reinforced Composite Brazing Alloy Tape

  WANG Zhiping, YANG Sinan, LIU Yan, DING Kunying, ZHANG Hui

  Materials For Mechanical Engineering. 2018, 42(10): 13-17,23. https://doi.org/10.11973/jxgccl201810003

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  SiC_p reinforced Ag-Cu-Ti (SiC_p/Ag-Cu-Ti) composite brazing alloy tapes with 10vol%-40vol% SiC_p were fabricated by tape casting technique, and then the SiC ceramics were brazed with the sandwich structure of Ag-Cu-Ti alloy foil/(SiC_p/Ag-Cu-Ti composite brazing alloy tape)/Ag-Cu-Ti alloy foil. The microstructure and micro area composition of the brazed joint were studied, and the flexural strength at room temperature and elevated temperature were measured. The results show that the SiC_p, which was coated by a layer of reaction product with thicknesses of 0.6-0.8 μm, distributed uniformly in the braze metal. The SiC ceramics were tightly bonded to the braze metal. An interface reaction layer composed of TiC and Ti₅Si₃ with thicknesses of 0.75-0.90 μm was formed between the SiC ceramics and the braze metal. With the increase of SiC_p content in the composite brazing alloy tape, the flexural strength at room temperature of the joint decreased slightly and then increased, and reached the maximum value of 301 MPa when the SiC_p content was 40vol%. In addition, the high-temperature flexural strength at 600℃ reached 193 MPa, which was obviously higher than that of ordinary brazed joints without SiC_p reinforcement.
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  Microstructure of Ti(C,N)-based Cermet and 45 Steel Joint Brazed with Multi-layered Composite Filler

  HE Hu, DU Xueming, YAO Zhenhua, PENG Junbo

  Materials For Mechanical Engineering. 2018, 42(10): 18-23. https://doi.org/10.11973/jxgccl201810004

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  With the multi-layered composite filler composed of Ag-Cu-Ti+Mo brazing alloy, copper foil and Ag-Cu brazing alloy, Ti(C,N)-based cermet and 45 steel was joined by vacuum brazing at different temperatures (890, 920, 950℃) for different times (10, 20, 30 min). The optimum brazing temperature and holding time were determined on the basis of cross-section morphology and shear strength of the joint. The microstructure on cross-section of the joint brazed with the optimum process was analyzed. The results show that with the increase of brazing temperature or the holding time, the interface reaction layer between the Ag-Cu-Ti+Mo brazing alloy and the cermet was thickened. The amount of Cu-Ti intermetallic compound in the reaction layer and that of Cu-based solid solution in brazing alloys at both sides increased. Also the shear strength of the joint increased and then decreased. The optimum brazing process was as follows:brazing temperature of 920℃ and holding time of 20 min. The joint obtained with the optimum process had the largest shear strength, whose structure was composed of Cu₃Ti₂+Ni₃Ti intermetallic compounds, Ag-based solid solution+Cu-based solid solution+Mo+CuTi intermetallic compound, Cu, and Ag-based solid solution+Cu-based solid solution, in order from the cermet to 45 steel.
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  Microstructure and Properties of Al-Ti-TiB₂ Laser-Cladding Layer on Surface of AZ31 Magnesium Alloy

  LIU Dekun, ZHANG Kemin, LIU Yingrui

  Materials For Mechanical Engineering. 2018, 42(10): 24-28,33. https://doi.org/10.11973/jxgccl201810005

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  Mixed powders of aluminum, titanium, TiB₂ with mass ratio of 1.0:3.0:0.5 were cladded on surface of AZ31 magnesium alloy by using a high energy laser with different powers (2.5, 3.0 kW). The microstructure, phase composition, hardness and corrosion resistance of the cladding layer were studied. The results show that during the laser cladding, the aluminum reacted with the titanium to form Al₃Ti phase. Meanwhile, the aluminum reacted with the magnesium to form Al_0.56Mg_0.44 phase and Al₁₂Mg₁₇ phase at the laser powers of 2.5 kW and 3.0 kW, respectively. The TiB₂ retained the original crystal structure. The cladding layer had a finer Al₃Ti phase at the laser power of 3.0 kW than at the laser power of 2.5 kW, and showed a better metallurgical bonding by the formation of a eutectic structure layer between the cladding layer and the magnesium alloy substrate. The laser power had little influence on the hardness of the cladding layer; the hardness increased and then decreased with the distance to the surface increasing. The laser cladding can effectively improve the corrosion resistance of AZ31 magnesium alloy. The corrosion resistance of the cladding layer at the laser power of 3.0 kW was better than that at the laser power of 2.5 kW.
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  Effect of Co Addition on Soft Magnetic Properties of FeCuNbSiB Amorphous/Nanocrystalline Magnetic Cores

  LI Jiuming, WANG Tongshuai, LIU Qirui, JIANG Daguo

  Materials For Mechanical Engineering. 2018, 42(10): 29-33. https://doi.org/10.11973/jxgccl201810006

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  B was substituted by Si and Co on basis of the composition of Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy, and then Fe_73.5Co_0.3Cu₁Nb₃Si_14.2B₈ alloy strips were prepared by single roll fast quenching method. The tested alloy strips were winded into toroidal magnetic cores, and then these cores were annealed at different temperatures. The influence of Co addition on the crystallization behavior of alloy strips and soft magnetic properties of magnetic cores were studied. The results show that Co addition had little effect on crystallization behavior of alloy strips. The tested alloy strips had an amorphous structure, and the magnetic cores after annealing at 550℃ had the co-existence of amorphous and nanocrystalline structures. After addition with Co, the initial permeability and saturation induction density of tested alloy amorphous/nanocrystalline magnetic cores were reduced by 0.149 9 H·m^-1 and 388 T, respectively, while the coercivity increased by 0.338 5 A·m^-1, indicating the direct-current soft magnetic properties decreased. The effective amplitude permeability, inductance and quality factor at high frequencies (less than 100 kHz) of tested alloy amorphous/nanocrystalline magnetic cores increased while the total loss density and coercivity decreased, indicating the alternating-current soft magnetic properties were improved.
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  Microstructure and Friction and Wear Performance of Ni35 Alloy Laser-Cladding Layer Reinforced by Ni-Coated SiC_p

  BAI Yan, PAN Chenggang, DING Zizheng

  Materials For Mechanical Engineering. 2018, 42(10): 34-40,45. https://doi.org/10.11973/jxgccl201810007

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  Ni-coated SiC_p reinforced Ni35 alloy laser-cladding layer was prepared on surface of H13 die steel substrate by laser cladding technique. The microstructure and the friction and wear performance at 25, 600℃ of the cladding layer were studied. The results show that the cladding layer was composed of γ-Ni(Fe)+M₃(B, Si) eutectic phase, M₂₃C₆ carbide, M₇C₃ carbide, Ni₃₁Si₁₂ nickel-silicide, and graphite. After friction and wear at different temperatures, the cladding layer had a higher surface microhardness and a lower wear volume than the substrate. The wear resistance at 25℃ of the cladding layer was improved greatly comparing with that of the substrate, and the improvement effect was higher than that at 600℃. The wear mechanism at 25℃ of the cladding layer was mainly micro-abrasive wear and adhesive wear, while that at 600℃ was abrasive wear, adhesive wear and slight oxidation wear.
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  Effect of NiCrAlY Alloy Powder Addition Amount on Microstructure and Properties of High Velocity Oxygen Fuel Sprayed WC-10Co4Cr Coating

  SI Yongli, WANG Xingfu, HAN Fusheng, LI Zhizhong, FENG Guobao

  Materials For Mechanical Engineering. 2018, 42(10): 41-45. https://doi.org/10.11973/jxgccl201810008

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  The NiCrAlY alloy powder with different mass fractions (0,6.5wt%,10.0wt%,20.0wt%) was added into the WC-10Co4Cr cermet powder, and then NiCrAlY/WC-10Co4Cr cermet coatings were prepared on surface of 316L stainless steel substrate by high velocity oxygen fuel spraying technique. The effects of the alloy powder addition amount on the microstructure, microhardness and corrosion resistance of the coatings were investigated. The results show that the microstructures of the coatings with different addition amounts of the alloy powder were mainly composed of WC phase. With the increase of addition amount of the alloy powder, the content of Ni and Ni₃Al phases in the coating increased, the porosity and hardness of the coating decreased, and the corrosion resistance increased and then decreased. When the mass fraction of the alloy powder was 6.5%, the coating had the highest uniform distribution of the hardness and the best corrosion resistance.
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  Effect of Glass Content on Properties of Low-Temperature Sintered Borosilicate Glass-AlN Ceramic Composite

  XU Jianfeng

  Materials For Mechanical Engineering. 2018, 42(10): 46-50,76. https://doi.org/10.11973/jxgccl201810009

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  With glass powder composed of 15wt%B₂O₃-45wt%MgO-35wt%SiO₂-5wt%ZrO₂ (BMSZ) and AlN powder as raw materials, BMSZ glass-AlN ceramic composites containing different glass content (55wt%-80wt%) were prepared by conventional pressureless sintering. The effects of glass content on the sintering performance, thermal properties, dielectric properties and mechanical properties were discussed. The results show that after adding the glass powder into the AlN powder and then being sintered at 775-875℃, the dense composites were obtained. Increasing the glass content properly improved the sintering densification. When the glass content exceeded 70wt%, the addition of glass weakened its role to promote the sintering densification, and deteriorated the thermal conductivity and bending strength of the composite, but appropriately reduced the dielectric loss of the composite. When the glass content was 70wt%, the composite sintered at 825℃ had a dense structure and obtained the best comprehensive performance, with the bulk density of 2.84 g·cm^-3, the relative thermal conductivity of 9.12 W·m^-1·K^-1, the dielectric constant of 7.65, the dielectric loss angle tangent of 1.24×10^-3, and the bending strength of 174.88 MPa.
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  Effect of Overmatching and Undermatching on Microstructure and Mechanical Properties of G115/T92 Dissimilar Steel Joint

  LI Linping, LIANG Jun, ZHAO Lei, XU Lianyong

  Materials For Mechanical Engineering. 2018, 42(10): 51-57. https://doi.org/10.11973/jxgccl201810010

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  The dissimilar steel welding was conducted on G115 steel and T92 steel with overmatching and undermatching welding materials, respectively. The effects of overmatching and undermatching on the microstructure and mechanical properties of the two joints were investigated. The results show that the microstructures in weld and heat-affected zone of the two joints consisted of typical tempered martensite. The content of δ-ferrite near the fusion line at T92 steel side in the overmatching joint was higher than that in the undermatching joint. The average volume fractions of δ-ferrite were both less than 0.3%.The dilution of W, Co, Mo and Cu was observed in the fusion zone at T92 steel side in overmatching joint and at G115 steel side in undermatching joint. The microhardness profile on cross-section of the two joints was W-shaped, and the hardness fluctuation in the overmatching weld was relatively large. The tensile strength and yield strength at room temperature and at 650℃ of the undermatching joint were higher than those of the overmatching joint. The impact toughness in the weld of the two joints was the poorest. The impact fracture of the weld in overmatching joint showed a quasi-cleavage fracture mechanism and that of the weld in undermatching joint showed a microvoid coalescence/quasi-cleavage mixed fracture mechanism.
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  Compressive Property of Knitted-Dapped Metal Rubber at Different Temperatures

  LI Tuo, BAI Hongbai

  Materials For Mechanical Engineering. 2018, 42(10): 58-61. https://doi.org/10.11973/jxgccl201810011

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  Static and dynamic compression tests at different temperatures (25, 100, 200, 300℃) were carried out on knitted-dapped metal rubber specimens. The effects of parameters, such as temperature, frequency and amplitude, on the compressive propery were studied. The results show that the stiffness and damping of the specimen decreased and then increased with the increase of temperature. The higher the density or the larger the deformation of the specimen, the more significant the effect of temperature on the static stiffness. With the increase of frequency, the dynamic stiffness of the specimen decreased slightly and the damping changed slightly. With the increase of the amplitude, the dynamic stiffness of the specimen decreased and the damping increased.
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  Effect of Zr Modification on Solid Particle Erosion Property of Silicide Coatings

  LI Xuan, LI Yinfeng, LI Tao, XIE Wenling

  Materials For Mechanical Engineering. 2018, 42(10): 62-66,71. https://doi.org/10.11973/jxgccl201810012

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  Pure silicide coating and Zr modified silicide coating were prepared on surface of TC4 alloy by diffusion penetration with the penetration agent composed of 15Si-5NaF-80Al₂O₃ and 15Si-10Zr-5NaF-70Al₂O₃ (mass fraction/%), respectively. The microstructure and the solid particle erosion resistance at diffrerent errosion angles of the two coatings were studied and compared. The results show that the two coatings consisted of three layers, including an outer layer composed of (Ti,X)Si₂ (X=Al, V or Zr) phase, a middle layer composed of TiSi phase and an inner layer composed of Ti₅Si₄ and Ti₅Si₃ phases. The Zr modified silicide coating had a relatively dense structure, and no cracks existed. The erosion rate of the two coatings increased with the increase of the erosion angle, and the Zr modified silicide coating showed a better solid particle erosion resistance than the pure silicide coating. The Zr modification improved the solid particle erosion resistance of the silicide coating more significantly at a high erosion angle than at a low erosion angle.
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  Effect of ZrB₂-SiC Composite Powder Addition Amount on Performance of Low Carbon Magnesium Carbon Refractory

  GE Shengtao, CHENG Feng, BI Yubao, LI Saisai, TAN Cao, WANG Junkai, ZHANG Haijun

  Materials For Mechanical Engineering. 2018, 42(10): 67-71. https://doi.org/10.11973/jxgccl201810013

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  By the replacement of flake graphite with ZrB₂-SiC composite powder, ZrB₂-SiC/MgO-C refractories were prepared after curing at 473 K for 12 h, and then heat treated at 1 373 K and 1 673 K, respectively. The effects of addition amount (0-4.0 wt%) of the composite powder on the physical properties, mechanical properties and thermal shock resistance of the refractories were studied. The results show that with the increase of addition amount of the composite powder, the modulus of rupture and compressive strength at ambient temperature of the refractories after curing and after heat-treatment increased and then decreased. The heat-treatment temperature had little effect on the physical and mechanical properties at ambient temperature. The modulus of rupture at elevated temperature of the refractories after heat-treatment at 1 673 K increased and then decreased with the increase of addition amount of the composite powder. The refractory after heat-treatment at 1 673 K mainly deformed in elasticity at testing temperatures below 673 K and in plasticity at testing temperatures no lower than 673 K. The replacement of graphite with ZrB₂-SiC composite powder greatly improved the thermal shock resistance in the oxidization atmosphere of the refractory.
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  Properties of Si₃N₄/SiC Refractory Prepared by Cr₂O₃ Catalyzed Nitridation

  HAN Lei, ZHAO Wanguo, LI Faliang, ZHANG Jun, ZENG Yuan, ZHANG Haijun

  Materials For Mechanical Engineering. 2018, 42(10): 72-76. https://doi.org/10.11973/jxgccl201810014

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  With SiC powder and silicon powder as raw materials, in-situ synthesized Cr₂O₃ as catalyst, Si₃N₄/SiC refractory was prepared by catalytic nitridation. The effects of catalyst addition amount and nitridation temperature on the phase composition, micromorphology, physical properties and mechanical properties of the refractory were investigated. The results show that when the nitridation temperature was 1 673 K and the Cr₂O₃ content (mass ratio of Cr₂O₃ to silicon powder) reached 3wt%, the silicon powder was completely nitrided; the refractory was composed of grain-like SiC, whisker-like α-Si₃N₄ and β-Si₃N₄. With increasing content of Cr₂O₃, the amount and length of Si₃N₄ whisky increased; the refractory became densification. With the rise of nitridation temperature, the flexural strength and compressive strength of the refractory increased. When the nitridation temperature was 1 673 K and the Cr₂O₃ content was 3wt%, the flexural strength and compressive strength reached the largest values of 34 MPa and 132 MPa, respectively.
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  Microstructure and Property of Diffusion Welded Titanium Alloy/Stainless Steel Joint with Nb and Cu as Composite Interlayer

  CHEN Yifan, ZHANG Zhanling, QIU Ranfeng

  Materials For Mechanical Engineering. 2018, 42(10): 77-80,86. https://doi.org/10.11973/jxgccl201810015

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  With Nb sheet and Cu sheet as composite interlayer materials, the vacuum diffusion welding was carried out on TC4 titanium alloy and 15-5PH stainless steel on a Gleeble-1500 thermomechanical simulator. The tensile strength of the joint was tested. The morphology at the interface and of the tensile fracture of the joint was observed, and the micro area composition was analyzed. The results show that the composite interlayer of Nb and Cu was helpful to restrain the interdiffusion of Ti, Fe and Cr, which came from titanium alloy and stainless steel. The strong bonding at stainless steel/Cu, Cu/Nb and Nb/titanium alloy interfaces was formed by atomic diffusion. A small amount of fine Nb-Fe intermetallic compound was formed at the Cu/Nb interface, which had little effect on the tensile strength of the joint. The maximum tensile strength reached 540 MPa. During tensile fracture the cracks propagated through the Cu layer, the Nb layer and the intermetallic compounds.
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  Sound Insulation Property of Aluminum Foam Sandwich Panel and Its Optimization

  XU Qiuting, ZHANG Xuefei, LI Ye, WANG Jiazheng, DENG Xin

  Materials For Mechanical Engineering. 2018, 42(10): 81-86. https://doi.org/10.11973/jxgccl201810016

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  A sound insulation prediction model of the aluminum foam sandwich panel was established on the basis of statistical energy analysis method, and verified by experiments. The effects of density and thickness of the aluminum foam on sound insulation property of the sandwich panel were predicted by the model. The acoustic vibration characteristics of the sandwich panel were analyzed. The sound insulation property of the sandwich panel was optimized by installation of damping layer. The results show that with the density of the aluminum foam increasing, the sound reduction index of the aluminum foam sandwich panel had relatively large increase amplitudes at low and medium frequencies and relatively small increase amplitudes at high frequencies. With the thickness of the aluminum foam increasing, the sound reduction index had relatively large increase amplitudes at medium frequencies and relatirely small increase amplitudes at low and high frequencies. The weighted sound reduction index increased with the density or the thickness of the aluminum foam increasing, but the increase amplitude decreased. When a 0.8 mm thick damping layer was placed in the middle of the aluminum foam, the weighted sound reduction index was effectively improved by 2.8 dB.